This invention relates to the field of data recording and playback and, more particularly, to improvements in apparatus for controlling the radial position of a write/read head relative to a data storage disk so that information can be written on (or read from) a desired data track.
Heretofore, a variety of radial access mechanisms have been proposed and utilized for controlling the radial position of a write/read head relative to the recording surface(s) of data storage disks (e.g. magnetic, magneto-optic, and optical disks). Typically, such mechanisms function to advance the head along straight or circular trajectories in a plane parallel to the plane of disk rotation. For straight head motion, both stepping and linear motors of various designs have been used. With a stepping device, the rotary motion of the motor shaft is commonly converted to linear motion by a lead screw, rack and pinion combination, or quite often, by a split band wrapped around the motor shaft. Stepping motors are also used in circular trajectory schemes. For a linear motor, its motion is directly coupled to a movably-mounted carriage which supports the head. In most cases, regardless of the driving scheme, the head carriage is suspended by a number of bearings or bushings that require precise alignment and high precision in parts manufacture to avoid the problems associated with backlash and friction.
In U.S. Pat. No. 4,426,669, issued to P. Bryer, there is disclosed a bearingless, backlash-free radal access mechanism which incorporates two pairs of flat or planar flexure members. One pair of flexure members serves to support a movable carriage on which a write/read transducer is mounted. The other pair serves to support the first pair, thereby enabling the carriage to move along a linear path. The carriage also supports a voice coil or the like which is disposed in a permanent magnetic field and surrounds a magnetizable stator. By applying current to the coil, the coil (and its supporting carriage) is advanced in one direction or the other in the magnetic field, such movement being limited to a linear path by the flexure members.
While the radial access mechanism disclosed to the aforementioned patent affords several advantages over those mechanisms employing bearings and bushings, it is a relatively large in physical size and, hence, does not lend itself for use in small disk drives.